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A130496
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Repetition of even numbers, with initial zeros, five times.
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0
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0, 0, 0, 0, 0, 2, 2, 2, 2, 2, 4, 4, 4, 4, 4, 6, 6, 6, 6, 6, 8, 8, 8, 8, 8, 10, 10, 10, 10, 10, 12, 12, 12, 12, 12, 14, 14, 14, 14, 14, 16, 16, 16, 16, 16, 18, 18, 18, 18, 18, 20, 20, 20, 20, 20, 22, 22, 22, 22, 22, 24, 24, 24, 24, 24, 26, 26, 26, 26, 26, 28, 28, 28, 28, 28, 30, 30, 30
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,6
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FORMULA
| a(n)= -2 + 2*Sum_{k=0..n} {[8*(sin(2*Pi*k/5))^2-5]^2-5}/20, with n>=0. a(n)= -2 + 2*Sum_{k=0..n} 1/50*{-9*[k mod 5]+[(k+1) mod 5]+[(k+2) mod 5]+[(k+3) mod 5]+11*[(k+4) mod 5]}, with n>=0.
a(n)=-2+2*Sum{k=0..n}{1-(k^4 mod 5)}, with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Feb 17 2010]
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MAPLE
| P:=proc(n) local i, j, k; for i from 0 by 1 to n do j:=-2+2*sum('(8*(sin(2*Pi*k/5))^2-5)^2-5', 'k'=0..i)/20; print(j); od; end: P(100);
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CROSSREFS
| Cf. A122461.
Sequence in context: A064133 A160675 A105674 * A187243 A001299 A001300
Adjacent sequences: A130493 A130494 A130495 * A130497 A130498 A130499
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KEYWORD
| easy,nonn
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AUTHOR
| Paolo P. Lava & Giorgio Balzarotti (paoloplava(AT)gmail.com), May 31 2007
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